RigidRaider,
I can't tell you about the Texecom Exodus 4 wire sensor, but .......I can tell you about the Apollo integrated base sounder, as I've just started to read up on Apollo stuff for an alarm installation.
Although you don't say which range the Apollo sensor is from, it IS one of the networked ones by the connections you name and the tag with the 'bobbles' on. L1 & L2 would connect this to the alarm network which carries both data and power over the same pair of wires. The tag with the bobbles on determines which address the sensor is present at on the network. The missing bobbles determining the specific address, and it lives on the back plate so the address is associated with a physical position not a particular sensor, which maybe swapped for another in the future.
As this sounder responds to network data from a fire panel, and the data is probably (i would hope!) check-summed, and its electrical/electronic design would (should!) in theory make it highly resistant to electrical disturbances, I would of thought it's highly unlikely that you'd be able to gets its sounder to trigger by 'mistake'. If you can I would question its design.
-clears throat- What your son REALLY needs....... but you might dispute this for fear of loosing your sanity, is a conventional alarm sounder which, when it's powered up, or triggered by seperate wires, will sound for him. I can't make any recommendations of make/model as I'm new to alarms and only interested in the networkable stuff, but hopefully this forum should be full of folks who will.
On the subject of christmas tree power supplies.....
Whilst these power supplies often carry various approval markings, in reality they are often poor quality inside. Sometimes dry soldered joints, full of hot melt glue like adhesives etc etc. It goes with the territory I'm afraid, cheap tat made down to a price. And it also runs the risk of being one of the many dodgy far eastern built electrical goods which escapes the UK's inspection bodies.
Can I make a recommendation here, as your son is so enthusiastic about experimenting, of a way to go with this?
Get him something called a bench power supply. These plug into the mains and then provide a variable voltage/s out, usually upto about 30v and currents commonly upto about 2 Amps. The important thing is though that if you stick to a good make (eg Hewlett Packard or Thurlby Thandar + others) then the safety will be much better and they're also built to take the abuse, especially being shorted out on a regular basis. Ebay is a good source for them and at a guess maybe about £50-£80 2nd hand. Just the same kind of thing they have on the lab bench in schools. Often they have analogue or digital meters on the front for voltage & current and this will help educate him as to the relationship between the two. But limit him to about 30 volts.
They also produce a DC (for that read: stable and non varying with time) voltage which is much more use to him for experimenting than AC is.
I don't know if £50-£80 ish is too much but I do feel that there's something much more than money at stake here; There's a little lad who's enthusiastic about stuff which might so easily lead to a future career. Too many kids these days are sat in front of computers and are not being creative with hands on things. If interest wanes you could always resell it. If you need it inspecting and checking out before the little fella gets it I'd be willing to do that for you.
It takes more componentry to produce a DC voltage from AC mains than to produce a lower AC voltage which simply requires a transformer. So I'm guessing your xmas tree light transformer is outputting 12v AC (for that read: varying - sinusoidally and at a frequency of 50Hz) and hence the reason why it won't read anything on a DC voltmeter.
@Alarm,
I roared laughing at your post when you said about you with the pressure mat and your mum when you were aged 11. And my mum thought it was just me at that age! Poor girl was a nervous wreck at one point. Most of the doors in my room had reed contacts on them too wired to bells.
But ....Jeeeez you must of been posh to of had a REAL pressure mat... lol...I had to make my own from foam and tin foil.
I bet loads of careers start in that way. God bless bells and pressure mats.